Heat exchangers

ABSTRACT

A baffle for a shell and tube heat exchanger comprises a one piece helical flight extending from a central core. The helical flight has a plurality of aligned openings for receiving tubes of the heat exchanger. The helical flight may be made by machining from a casting or solid block of material, or by an additive manufacturing process.

FOREIGN PRIORITY

This application claims priority to European Patent Application No.15461569.4 filed 23 Oct. 2015, the entire contents of which isincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to heat exchangers.

BACKGROUND

Heat exchangers are used in a wide range of applications and come in avariety of forms. One form of heat exchanger is a shell and tube heatexchanger. In such a heat exchanger, a plurality of tubes extendsthrough a shell. A first fluid is admitted to and flows through theshell and a second fluid is admitted to the tubes. The first and secondfluids are separated from one another by the walls of the tubes and heattransfer from one fluid to the other takes place through those walls. Insome constructions, the first fluid is guided through the shell in aprescribed flow path by means of a baffle, for example a helical baffle,in order to increase the length of the flow path and thereby improveheat transfer.

However, it would be desirable to provide a shell and tube heatexchanger which provides satisfactory heat transfer and which isdurable.

SUMMARY

From a first aspect there is provided baffle for a shell and tube heatexchanger comprising a one piece helical flight extending from a centralcore, the helical flight having a plurality of openings for forming aplurality of fluid flow passages through the flight.

From a further aspect of this disclosure, there is provided a shell andtube heat exchanger comprising a shell having an inlet and an outlet fora first fluid; a plurality of tubes extending through the shell andhaving an inlet and outlet for a second fluid; and a baffle arranged insaid shell and having a one-piece helical flight extending from acentral core, said helical flight having a plurality of openings throughwhich the tubes extend or are aligned for forming a plurality of fluidflow passages through the flight.

The helical flight may be integrally formed with the core or may beattached to it by suitable means, for example brazing or welding.

The core may be a solid core, although in some embodiments, the core maybe hollow, for example for conducting a fluid.

The baffle may further comprise a plurality of tubes mounted through theopenings in the flight for conducting fluid therethrough.

In an alternative embodiment, the baffle may further comprise aplurality of tubes integrally formed with the flight and aligned withthe openings in the flight for conducting fluid therethrough.

The heat exchanger may be a counterflow heat exchanger, in which thefirst and second fluids flow in opposite directions through the heatexchanger or a parallel flow heat exchanger in which the first andsecond fluids flow in the same direction through the heat exchanger.

The disclosure also provides a method of manufacturing a heat exchangerbaffle comprising a helical flight extending from a central core,comprising manufacturing the flight as a single continuous piece, andforming a plurality of holes in the flight for forming a fluid flowpassage through the flight.

The helical flight may be integrally formed with the core.Alternatively, the flight may be made separately from the core andattached to the core by suitable means, for example brazing or welding.

The flight may be made in a number of ways.

In one embodiment, the flight may be rough cast and then machined to afinal shape, the holes being produced by a suitable mechanism, forexample drilling. The holes may be formed before or after machining theflight.

In another embodiment, the flight may be machined from a block ofmaterial, for example a cylindrical bar, and the holes being produced inan appropriate manner, e.g. drilling. Again, the holes may be formedbefore or after machining the flight

In either of the above arrangements, should the core be integrallyformed with the flight, the core may be machined to create a centralpassage therethrough should that be required.

In an alternative embodiment, the flight may be made by an additivemanufacturing process. Using this approach, the holes in the flight and,optionally, the core may be produced simultaneously with the flight.

In one embodiment, the method may further include forming a plurality oftubes in alignment with and joining the holes simultaneously with theflight by the additive manufacturing process.

The disclosure also extends to a method of manufacturing a heatexchanger comprising manufacturing a helical baffle by any of theadditive manufacturing processes disclosed above and forming a heatexchanger body around the helical baffle simultaneously with the flightby the additive manufacturing process.

A non-limiting embodiment of the disclosure will now be described withreference to the accompanying drawings.

BRIEF DECSRIPTION OF DRAWINGS

FIG. 1 shows a perspective, cut away view of a shell and tube heatexchanger in accordance with this disclosure

FIG. 2 shows a perspective view of a baffle in accordance with thedisclosure; and

FIG. 3 shows a perspective view of the baffle of FIG. 2 with tubesinstalled.

DETAILED DESCRITION

With reference to FIG. 1, a shell and tube heat exchanger 2 comprises ashell 4 having a tubular body portion 6 having an inlet 8 for a first(for example hot) fluid and an outlet 10 for the first fluid.

The tubular body portion 6 is formed with end walls 12, 14 which closethe shell 4 to form a shell cavity 16. One or both of the end walls12,14 may be initially separate from the tubular body 6 and attachedthereto during assembly of the heat exchanger. The end walls 12, 14 haveholes 18 for receiving, in a plurality tubes 20 which extend through theshell cavity 16 and a central opening 22 for receiving the core 24 of ahelical baffle 26. The helical baffle 26 creates a helical flow path forthe first fluid through the shell cavity 16.

The tubes 20 extend from an inlet plenum 28 for a second (for examplecold) fluid provided at one end of the tubular body portion 6 to anoutlet plenum 30 provided at the opposite end of the tubular bodyportion 6. In this embodiment, the inlet and outlet plenums 28, 30 areformed as closed caps mounted to the end walls 12, 14 and havingrespective base walls 32, 34 with openings 36 aligned with the holes 18,20 in the end walls 12, 14 for receiving the tubes 20 and central core24 in a sealed manner. In this embodiment, respective o-ring seals maybe provided around the tubes 20 and core 24, although other suitablesealing mechanisms may be used. Also, it will be appreciated that theplenums may be provided in any suitable fashion, for example as opencaps or by suitable partitioning of the tubular body portion 6.

Turning now to FIGS. 2 and 3, the helical baffle 26 will be described ingreater detail.

The helical baffle 26 comprises core 24 from which extends a one-piecehelical flight 38. In this embodiment, the core 24 is hollow and hasopen ends and may allow for passage of the second fluid from the inletplenum 28 to the outlet plenum 30. However, in other embodiments, theends of the core 24 may be closed to prevent passage of fluidtherealong, or the core 24 may be solid.

The helical flight 38 extends from the radially outer surface 40 of thecore 24. In this embodiment, the core 24 is formed integrally with theflight 38, but in other embodiments, the flight 38 may be manufacturedin one piece separately from the core 24 and subsequently attached tothe core 24, for example by brazing.

The flight 38 comprises an array of aligned holes 42 for receiving thetubes 20, as illustrated in FIG. 3, so as to form a plurality of fluidpassages through the flight 38. By aligned is simply meant that theopenings 42 are positioned to receive the tubes 20. In this embodiment,the openings 42 and the tubes 20 are aligned parallel to the axis of thecore 24 in this embodiment, although this is not essential. For examplethe openings 42 and the tubes 20 may extend at an angle to the axis ofthe core. The tubes 20 may be located in the holes 42 in any suitablemanner, for example brazing.

The helical flight 38 at least is made in a single piece. This mayprovide a number of advantages. Firstly, it may provide a smoother flowpath for the first fluid through the shell cavity 16, leading to a lowerpressure drop in the first fluid. Secondly, the flight may be moredurable than a multi-piece baffle which will, by necessity, havemultiple joints, leading to possible weaknesses, particularly when beingsubjected to high pressure flow.

The advantages may be even more pronounced in embodiments where thehelical flight 38 and the core 24 are formed in one piece, as it avoidspossible weaknesses at the joint between the flight 38 and the core 24.

The flight 38 (with, optionally, the core 24) may be made in one pieceby any suitable method.

In a first embodiment, the flight 38 (and core 24 where present) mayfirst be rough cast, for example to a near-net shape, and then machinedto a final shape. The holes 42 may then be produced in the flights by asuitable process. For example the holes 42 may be drilled, formed by EDM(electro-discharge machining) or any other suitable process. It is notessential that the holes 42 be created after the flight 38 has beenmachined. Thus, in another embodiment, the holes 42 may be produced inthe rough cast flight prior to final machining of the flight 38. Roughholes may be rough cast into the rough casting to facilitate subsequentmachining of the holes 42.

In another embodiment, the flight 38 (and core 24 where present) may bemachined to a final shape from a block of material, for example acylindrical bar. The holes 42 may then be formed as above. Thus, theholes 42 may be machined either in the machined flight 38 or in theprecursor block of material.

In either of the above arrangements, should the core 24 be integrallyformed with the flight 38, the core 24 may also be machined to create acentral passage therethrough should that be required. Again this may bedone either before or after machining of the flight 38.

In an alternative embodiment, the flight 38 with, optionally, the core24 (with or without a central passage) may be made by an additivemanufacturing process. Examples of such processes include, but are notlimited to, Direct Metal Laser Sintering (DMLS), Electron Beam Sintering(EBS), Electron Beam Melting (EBM), Laser Engineered Net Shaping (LENS),Laser Net Shape Manufacturing (LNSM), Direct Metal Deposition (DMD),Laser Powder Bed Fusion (LPBF), Selective Laser Sintering (SLS) andSelective Laser Melting (SLM).

An advantage of this technique is that it is potentially less wastefulof material. Also, it will allow the holes 42, and where present thecentral passage of the core 24, to be formed at the same time as theflight 38, avoiding the need to perform a separate drilling or otherprocess to create the holes 42 or core passage.

After the baffle 26 has been manufactured and the tubes 20 mountedthereto, it may be mounted in the shell cavity 16 in any suitablemanner, for example through an open end of the tubular body portion 6prior to attachment of the end wall(s) 12, 14.

In another embodiment, however, when using an additive manufacturingtechnique, the tubes 20 may be formed integrally with the baffle 26,avoiding the need for a separate process for assembling the tubes 20 inthe holes 42 in the flight 38.

In a yet further embodiment, not only may the tubes 20 be formedintegrally with the baffle 26, but also the heat exchanger body 6 couldalso be formed simultaneously with the baffle 26, avoiding the need forseparate mounting of the baffle 26 in the heat exchanger body 6.

It should be noted that the above is non-limiting a description of anembodiment of the disclosure and that modifications may be made theretowithin the scope of the disclosure. For example while in thisembodiment, the heat exchanger 2 is shown as a counterflow heatexchanger (the flows of the first and second fluids being in oppositedirections), the heat exchanger could also be a parallel flow heatexchanger.

1. A baffle for a shell and tube heat exchanger comprising: a one piecehelical flight extending from a central core, the helical flight havinga plurality of openings therethrough for forming a plurality of fluidflow passages through the flight.
 2. A baffle as claimed in claim 1,wherein the core is a hollow core, or is a solid core.
 3. A baffle asclaimed in claim 1, wherein the helical flight is integrally formed withthe core, or is formed separately from and attached to the core.
 4. Abaffle as claimed in claim 1 further comprising: a plurality of tubesmounted through the openings in the flight for conducting fluidtherethrough.
 5. A baffle as claimed in claim 1, further comprising; aplurality of tubes integrally formed with the flight and aligned withthe openings in the flight for conducting fluid therethrough.
 6. A shelland tube heat exchanger comprising; a shell having an inlet and anoutlet for a first fluid; a plurality of tubes extending through theshell and having an inlet and outlet for a second fluid; and a baffle asclaimed in any preceding claim arranged in said shell said tubesextending through or aligning with the plurality of openings in thehelical flight.
 7. A method of manufacturing a heat exchanger bafflecomprising a helical flight extending from a central core, comprising;forming the helical flight as a single continuous piece; and forming aplurality of holes in the flight for forming a fluid flow passagethrough the flight.
 8. A method as claimed in claim 7, wherein thehelical flight is integrally formed with the core.
 9. A method asclaimed in claim 7, comprising providing a rough casting of the helicalflight, machining the rough casting to a final shape, and forming theholes in the flight either before or after machining the flight.
 10. Amethod as claimed in claim 7, comprising providing a block of material,for example a cylindrical block, machining the block to produce a flighthaving a final shape, and forming the holes in the flight either beforeor after machining the flight.
 11. A method as claimed in claim 9,wherein the holes are formed by drilling.
 12. A method as claimed inclaim 7, comprising manufacturing the helical flight by an additivemanufacturing process.
 13. A method as claimed in claim 12, comprisingforming the holes simultaneously with the flight by the additivemanufacturing process.
 14. A method as claimed in claims 13, furthercomprising forming a plurality of tubes in alignment with and joiningthe holes simultaneously with the flight by the additive manufacturingprocess.
 15. A method of manufacturing a heat exchanger comprisingmanufacturing a helical baffle by a method as claimed in claim 12, andforming a heat exchanger body around the helical baffle simultaneouslywith the flight by the additive manufacturing process.